Solar heating systems in which a mirror moves with the passage of the sun through the sky relative to the earth are well known. Such installations frequently not only move the mirror between a morning and evening position for the sun but, also, to a "night" position in which the mirror has its mirror surface facing downwardly, so that it is protected against contamination, for example by dust, rain, snow or the like. As the mirror moves when following the sun, it tilts about an angle of about 180.degree. . For the night position, the mirror is placed in an upper dead center (UDC) position so that, considering the UDC position, the overall tilt angle of the mirror system will be about 250.degree. .
The tilt angle of 250.degree. , which must be followed by a flexible tube or hose, must be covered during 24 hours first in one direction and then, for return to the UDC position, in the other direction. A heat carrying medium, typically a fluid and especially a liquid medium, is circulated in the flexible tube. The flexible tube is coupled to a connecting flange or other fixed connecting position which usually is located outside of the angle of rotation of the mirror system. Entirely apart from the pure rotary movement, the flexible tube must also carry out a substantial swinging movement along a circular arc. The flexible hose is connected to the mirror system so that it must form a connection to the mirror as well as to the fixed connection for conducting the heated medium to a utilization position. It has been customary to use a metallic corrugated or accordeon-pleated flexible tube, surrounded by a mesh or woven material about which an insulating jacket is placed. The heat carrying medium is usually subjected to a pressure of about 20 bar, and may be subject to a temperature of between 300.degree. to 400.degree. C.
It has been found that, in operation, pleated or corrugated or similar flexible tubes have a lifetime which is substantially below that hoped for and expected. Most flexible tubes fail after 3000 and at best after 5000 cyles, by breakage of the tube. A suitable lifetime, however, is about 10,000 cycles.